A Unified Anisotropic Elasto-plastic Model for Sand

This paper presents a unified approach to model the influence of fabric anisotropy 6 and its evolution on both the elastic and plastic responses of sand. A physically based fabric 7 tensor is employed to characterize the anisotropic internal structure of sand. It is incorporated 8 into the nonlinear elastic stiffness tensor to describe anisotropic elasticity, and is further 9 included explicitly in the yield function, the dilatancy relation and the flow rule to characterize 10 the anisotropic plastic sand response. The physical change of fabric with loading is described 11 by a fabric evolution law driven by plastic strain which influences both the elastic and the 12 plastic sand behavior. The proposed model furnishes a comprehensive consideration of both 13 anisotropic elasticity and anisotropic plasticity, particularly the nonlinear change of elastic 14 stiffness with the evolution of fabric during the plastic deformation of sand. It also offers a 15 natural and rational way to capture the non-coaxial behavior in sand caused by anisotropy. It 16 also facilitates easy determination of the initial anisotropy in sand based on simple laboratory 17 tests and avoids the various arbitrary assumptions on its value made by many previous studies. 18 The model predictions on sand behavior compare well with test data. 19 20